I am buying a new video card and am now doubting between AMD and NVidia. As I won't be upgrading my processor and mainboard atm, but I want to play some bluray movies I think it is necessary that the video card can use hardware acceleration on Ubuntu.
With NVidia there is support as is for example demonstrated here with the libvdpau1
driver. Does similar things/drivers exist for the high-end AMD video cards like a HD6950?
(Note that I personally do not require an open source driver. If a binary driver will work, that is okay for me)
I spoke with AMD directly and learned that Yes, the HD6950 will support H.264 hardware acceleration on Ubuntu. Don't know the state of all AMD drivers but I was told the linux driver for Ubuntu that can be downloaded from the AMD website will get this done.
Some other info:
In general, the Radeon cards do support 2D and 3D acceleration as documented here: https://help.ubuntu.com/community/RadeonDriver
The NVIDIA drivers have historically been said to run better with Linux. However, AMD has been putting a lot of work into their Open Source drivers for the last year or more and unlike NVIDIA they provide documentation, limited support, and an actual active development initiative for free software. So the community is vocal about supporting AMD video cards with "your wallet."
For a comparison of AMD Radeon graphics cards, see this Phoronix article: http://www.phoronix.com/scan.php?page=article&item=amd_comp_oktoberfest&num=1
Blu-ray playback can be a little tricky on Ubuntu. You can read more here: https://help.ubuntu.com/community/RestrictedFormats/BluRayAndHDDVD
The Catalyst driver does provide that kind of acceleration through VA-API, but the challenge is that many programs do not take advantage of it. I believe Mplayer and VLC have the option to use VA-API, but Flash for example has not yet taken advantage of the support for this video acceleration API.
In terms of easier driver management, you might be better off with an ATI card, but in terms of better support for the latest video acceleration tech, then I would suggest nVidia. However, you can stick with ATI all the way if powerful graphics are your thing as well, as ATI (AMD) tends to be on top in terms of graphics (by just a minor edge).
Again, if you are looking for an easier, more well supported solution, then nVidia is the better choice.